Initial version of alpine docker

[adsharma]

This docker attempts to create an environment where an extension author can simply mount their extension within a pre-built image and get it to build.

This image doesn't quite do that yet. But hopefully a starting point for further discussion and feedback.

More context

Usage:

docker buildx build -t duckdb_ext_tools:latest . --load -f docker/linux_amd64/alpine/Dockerfile
docker run -v $(pwd):/duckdb_build_dir/my_extension --env-file=docker/linux_amd64/alpine/env.txt -it  duckdb_ext_tools:latest

[adsharma]

Couple of notes here:

I was able to mount an extension inside this docker and build it and run some tests.

However to make it more useful, we need to figure out:

• How to publish the built docker to docker hub or similar
• What should be inside such a image? Do we want to include ccache? All of duckdb build artifacts or only what's needed to build an extension?
• Now if the extension developer wants to build their own extension inside this docker, they'll have two extensions

/duckdb_build_dir/extension_docker_image_built_with
/duckdb_build_dir/my_extension

How does my_extension refer to the duckdb dir in extension_docker_image_built_with?

Perhaps we can first get this PR reviewed/merged and then discuss the issues above?